PB 180 Tunnel Vision

[basalgangster]

My Powerbook 180 powers up fine, but over the first 3-5 minutes of use, the screen turns dark at the corners, and progressively darkens the screen from the edges in. Everything else seems to be working great. Turning it off for a few minutes and starting it again temporarily cures it, and then it happens again. Any ideas?

 

[beachycove]

The only repair is to replace the screen.

 

[techknight]

or check out the SMD caps on the screen and replace those.

 

[Byrd]

Is replacing the caps on the screen going to actually do anything? I thought the "tunnel vision" was failure of the CCFL backlighting, which cannot be fixed.

 

[basalgangster]

Just after shutting down, when the backlighting should be off, I can still see the darkening at the edges. Does this make sense?

 

[beachycove]

A few years ago, I had a PowerBook Duo 280 that behaved just like this. I did a lot of looking on archived discussion boards, and asking around here, for a cure at the time.

As I recall, what I came up with was that the earliest active matrix greyscale LCDs found on the PowerBook 170 (I think), and certainly the 180, 270, and 280 (all the ones that have a "glassy" surface) are all prone to this, and that there is no known repair. But not all of them have the defect, so the fix is to find a working replacement LCD: my 180, for example, is absolutely fine, whereas my 280 still awaits a donor....

It is not a failure of the backlighting, but is apparently the result of a failure in the "edges" of the LCD itself. It is not merely a VRAM problem either, as in my 280, I went to the trouble of replacing the logic board with a known-good one from a working 280c: no joy, as the same problem resulted.

If you find out differently, do let us all know!

 

[beachycove]

And yes, just like your 180, my 280 also remained black at the edges after shutting down. It had to be left for 30 mins or so before it would start up clear, and then the black creep would start again. You could only use it for about 5 mins.

 

[techknight]

is it possible the actual liquid crystal is starting to degrade? remember LCD technology was in its infancy at the time as far as high-resolution displays. its possible?

 

[basalgangster]

Thanks for the information and advice. I swapped screens with a dead 180 (killed by leaky battery), and this one looks perfect. It's been on for almost an hour with no sign of darkening at the corners. I think the screen is a lot sharper too.